1. Field of the Invention
The present invention relates to a combination read/write thin film magnetic head used as a floating type magnetic head, and particularly to a combination read/write thin film magnetic head in which a shielding magnetic layer is provided on either side of a magnetic gap of an inductive thin film magnetic head in the direction of the track width thereof in order to suppress the occurrence of write fringing, and a manufacturing method thereof.
2. Description of the Related Art
FIG. 17 is a perspective view schematically showing the whole structure of a conventional combination read/write thin film magnetic head formed on a slider 10, and FIG. 18(a) is a partial front view showing the conventional combination read/write thin film magnetic head, as viewed from the side opposite to a recording medium.
The combination read/write thin film magnetic head shown in FIGS. 17 and 18(a) is formed at the trailing end of the slider 10 which constitutes a floating type head, and comprises a laminate of a reading head h1 and a recording inductive head h2.
The combination read/write thin film magnetic head further comprises a lower core layer 11 made of a magnetic material having high magnetic permeability, such as an Ni--Fe alloy (permalloy), sendust, or the like. In the combination read/write thin film magnetic head comprising the reading head h1 which employs a magnetoresistive element, and the inductive head h2 which is continuously laminated thereon, the lower core layer 11 functions not only as a core layer for the inductive head h2 but also as an upper shielding layer for the reading head h1.
On the lower core layer 11 is formed a gap layer 12 made of a non-magnetic material such as Al.sub.2 O.sub.3 (alumina) or the like. On the gap layer 12 is formed an insulation layer (not shown in the drawings) made of a resist material such as polyimide or the like or another organic material. On the insulation layer is spirally formed a coil layer 5 using an electrically conductive material having low electric resistance, such as Cu or the like. The coil layer 5 is formed so as to turn round the base end 3b of an upper core layer 3.
On the coil layer 5 is formed an insulation layer (not shown in the drawings) made of an organic resin material or the like. On the insulation layer is formed the upper core layer 3 by plating a magnetic layer such as permalloy or the like. In a portion opposite to the magnetic medium, the tip 3a of the upper core layer 3 is joined to the lower core layer 11 with the gap layer 12 therebetween to form a magnetic gap having a gap length G1. The base end 3b of the upper core layer 3 is magnetically connected to the lower core layer 11.
In the writing inductive head h2, when a recording current is supplied to the coil layer 5, a record magnetic field is induced in the lower core layer 11 and the upper core layer 3, and a magnetic signal is recorded in the recording medium such as a hard disk or the like by a leakage magnetic field from the magnetic gap portion between the lower core layer 11 and the tip 3a of the upper core layer 3.
In the writing magnetic gap of the inductive head h2, the gap length G1 is determined by the distance (i.e., the thickness of the gap layer 12) between the lower core layer 11 and the tip 3a of the upper core layer 3 joined thereto with the gap layer 12 therebetween. As shown in FIG. 18(a), the track width Tw is determined by the width of the tip 3a of the upper core layer 3.
As shown in FIG. 18(a), the width T2 of the lower core layer 11 is sufficiently larger than the width Tw of the tip 3a of the upper core layer 3. The reason why the width T2 of the lower core layer 11 is larger is that the area of the upper flat surface of the upper core layer 11 is increased to facilitate the formation of the coil layer 5 on the lower core layer 11 with the insulation layer therebetween, and at the same time, to increase the magnetic shielding effect on the magnetoresistive element layer 13 formed below the inductive head h2.
In the reading head h1 which employs magnetoresistance, the magnetoresistive element layer 13 is provided on a lower shielding layer 14 with a lower gap layer 15a therebetween, and the lower core layer 11 is formed on the magnetoresistive element layer 13 with an upper gap layer 15b therebetween, the magnetoresistive element layer 13 also serving as an upper shielding layer.
If the width T2 of the lower core layer 11 is larger than the width Tw of the tip 3a of the upper core layer 3, as shown in FIG. 8(a), when a record magnetic field is induced in the lower core layer 11 and the upper core layer 3, and a recording leakage magnetic field is generated between the tip 3a and the lower core layer 11, the leakage magnetic field is beyond the range of the width (track width) Tw of the tip 3a of the upper core layer 3, and affected by the width of the lower core layer 11 to bring about blots of the magnetic field on both sides of the width Tw.
FIG. 18(b) shows a recording pattern of the data recorded by using the magnetic head shown in FIG. 18(a). The recording pattern indicates that write fringing (writing blot) occurs out of the track width Tw. The occurrence of this write fringing makes it impossible to detect the track position on the written recording medium with high precision, and thus causes tracking servo error. Particularly, in high-density recording, the pitch of adjacent tracks is small, and thus write fringing has a significant effect.